A commonly accepted practice of removing solid particles from a flue gas includes the utilization of an electrostatic precipitator to hold the solid particles without inhibiting the flow of the flue gas. Typically, an electrostatic precipitator is positioned in the flue between the outlet of a boiler and a smokestack.
The ordinary construction of an electrostatic precipitator includes a plurality of large, flat, metal plates which are spaced from each other. The metal plates may have a height of up to 30 feet or more, and a width of up to 10 feet or more. It is to be appreciated that the specific size of the plates in a given precipitator is dependent upon the particular precipitator construction for a given application. Ideally, the flat plates are equidistantly spaced from each other. A second plurality of elongated electrodes is positioned among the plates. The electrodes are positioned between each pair of adjacent plates. The elongated electrodes are equidistantly spaced from adjacent plates.
The uniform spacing of the elongated electrodes from the plates is necessary to have a uniform electrostatic charge between the elongated electrodes and the plates. A uniform electrostatic charge generates uniform collection of solid particles on the plates. Typically, the solid particles are removed from the plates by rapping the plates to vibrate the plates and, thereby, cause the collected solid particles to drop off of the plates in clusters into collectors under the plates.
The flue gas which enters the electrostatic precipitator is hot. Commonly, additional heat enters the precipitator in the form of fires caused by problems in the operation of the boiler. The continual exposure of the plates to heat causes the plates to warp or buckle. The warping or buckling of the plates destroys the uniform spacing between adjacent surfaces of adjacent plates and the uniformed spacing between each of the elongated electrodes and the respective adjacent plates. Thereby, the effectiveness of the precipitator in removing solid particles from flue gas is reduced so that the precipitator has a lower capacity. Consequently, the capacity of the boiler, which produces the flue gas, must also be lowered to comply with emissions regulations. In the case of a power generation unit, as the capacity of the boiler is reduced, the capacity of a power generating system connected to the boiler is also reduced. In order to maintain an electrostatic precipitator fully effective, it is desirable to maintain the spaced plates of the precipitator in an equidistantly spaced relationship to each other and to the electrodes.
One apparatus for holding electrostatic precipitator plates in an equidistantly spaced relationship is taught in U.S. Pat. No. 4,007,023, issued Feb. 8, 1977, to Batza et al, entitled "Electrostatic Precipitator With Collector-electrode Spacers." The Batza et al patent discloses a spacer construction for use between adjacent collecting electrode strips to hold the strips apart an equal distance from each other. Each spacer includes a bracket which is fixed to one of the strips. A spacer body is connected to the bracket by a pivot. A second bracket is fixed to a second electrode strip. The spacer body includes a slot for receiving the second bracket. The Batza et al device is expensive to manufacture and difficult to install, since the two brackets must be perfectly aligned on facing surfaces. Furthermore, the Batza spacer provides many sharp edges which create localized electrostatic charges to distort the electrostatic field around the strips thereby reducing the effectiveness of the electrostatic precipitator. Another known spacer is one which has an "H" bar construction. This spacer has a disadvantage in that the spacer is made up of three separate pieces which are welded together. In particular, it has been found that there is sufficient variation in size of the spacers to create a misalignment of the plates. The variation in size cannot be easily adapted in the field.